Sec. 95.645 Control accessibility.
(a) No control, switch or other type of adjustment which, when manipulated, can result in a violation of the rules shall be accessible
from the transmitter operating panel or from exterior of the transmitter enclosure.
(b) An R/C transmitter which incorporates plug-in frequency determining modules which are changed by the user must be certificated
with the modules. Each module must contain all of the frequency determining circuitry including the oscillator. Plug-in crystals are not
considered modules and must not be accessible to the user.

So, is Futaba manufacturing illegal radios by making their crystals removable? I don't think so. The FCC is talking about changing the "72 MHZ" freq to say "35 MHZ" etc., not changing legitimate crystals in the RC band with which the transmitter was certified. With regards to Futaba, I have always stayed in the upper or lower band as they recommend with no issues with both AM and FM.

Sec. 95.645 Control accessibility.
(a) No control, switch or other type of adjustment which, when manipulated, can result in a violation of the rules shall be accessible
from the transmitter operating panel or from exterior of the transmitter enclosure.

This tells me Futaba and other's, removable freq crystals are within the rules of the FCC or they would not have been certified.